Method for forming Cube texture aluminum layer on surface of composite aluminum current collector

Abstract

The invention provides a method for forming a Cube texture aluminum layer on the surface of a composite aluminum current collector, and the method comprises the following steps: S1, providing a high-molecular base film, and carrying out plasma treatment on the surface of the high-molecular base film to form an active functional group; s2, an aluminum layer is deposited through a magnetron sputtering or vacuum evaporation method, the vacuum degree ranges from 0.5 * 10 <-3 > Pa to 5 * 10 <-3 > Pa, and the temperature of the macromolecule base film is controlled to range from 100 DEG C to 200 DEG C; s3, the aluminum deposition rate is controlled to be 50 nm / s-100 nm / s, the deposition temperature is controlled to be 50-200 DEG C, the deposition thickness is controlled to be 0.5-5 [mu] m, the crystal face {100} of the aluminum layer grows in the direction perpendicular to the surface of the macromolecule base film, and the 1t; 100 gt; s4, annealing treatment is carried out at the temperature of 100 DEG C to 200 DEG C under the inert atmosphere, heat preservation is carried out for 10 min to 30 min, in this way, the composite aluminum current collector with the Cube type texture as the main texture is obtained on the macromolecule base film, and a large number of lt arranged in parallel are formed in an aluminum layer through the Cube texture; 100 gt; and due to the crystal orientation channel, the electric conduction and heat conduction performances of the composite aluminum current collector are improved.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a method for forming a cube-textured aluminum layer on the surface of a composite aluminum current collector. Background Technology

[0002] Composite current collectors consist of an intermediate thin film layer and a conductive layer located on the surface of the intermediate thin film layer. Composite aluminum current collectors refer to composite current collectors with aluminum as the surface conductive layer. The surface contact resistance of the aluminum conductive layer in current composite aluminum current collectors is relatively high, which leads to local overheating during battery charging when using composite current collectors, resulting in thermal runaway. Summary of the Invention

[0003] In view of the shortcomings of the prior art, on the one hand, the purpose of the present invention is to provide a method for forming a cube-textured aluminum layer on the surface of a composite aluminum current collector, so as to solve the problem of thermal runaway caused by local overheating of the battery due to the high surface contact resistance of the composite current collector in the prior art.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A method for forming a cube-textured aluminum layer on the surface of a composite aluminum current collector includes the following steps: Step S1, providing a polymer base film, the surface of which is plasma-treated to form active functional groups; Step S2, depositing an aluminum layer using magnetron sputtering or vacuum evaporation at a vacuum level of 0.5 x 10⁻ Pa to 5 x 10⁻ Pa, with the polymer base film temperature controlled at 100°C to 200°C; Step S3, controlling the aluminum deposition rate at 50 nm / s to 100 nm / s, the deposition temperature at 50°C to 200°C, and the deposition thickness at 0.5 μm to 5 μm, ensuring that the {100} crystal plane of the aluminum layer grows perpendicular to the surface of the polymer base film, and that... <100> The crystal orientation is aligned along the mechanical direction of the polymer base film; Step S4: Annealing is performed at 100℃-200℃ under an inert atmosphere for 10min-30min.

[0005] Furthermore, in step S2, the temperature gradient of the polymer base film is controlled within ±5℃ / cm; in step S3, the deposition rate of the aluminum thin film is controlled within the range of 50-100nm / s, and the deposition temperature is controlled within the range of 50-200℃. High temperature promotes the migration of aluminum atoms and the directional alignment of grains.

[0006] Furthermore, the polymer base film is polyethylene terephthalate or polypropylene with carboxyl groups grafted onto its surface, and the surface roughness Ra ≤ 200 nm.

[0007] Furthermore, the cube texture of the composite aluminum current collector aluminum layer after annealing was tested by XRD using pole figure data to calculate the orientation distribution function (ODF). The diffraction intensity distribution was tested with the sample tilt angle from 30° to 75°. When the tilt angle was ≥50°, the measured cube texture volume fraction accounted for more than 80%.

[0008] Furthermore, using the XRD Scherrer formula, the grain size of the aluminum layer was calculated to be 10nm-50nm, and the proportion of grain boundary orientation difference angles ≤10° was >90%.

[0009] Furthermore, the proportion of cube-oriented grains in the aluminum layer is ≥80%; the deviation between the {100} crystal plane of the aluminum layer and the normal of the base film surface is ≤5°; the aluminum layer <100> The angle between the crystal orientation and the current collector mechanical orientation is ≤10°.

[0010] Furthermore, the resistivity within the aluminum layer is ≤3.5×10⁻ 8 Ω·m, with anisotropy coefficients of 0.95–1.05.

[0011] Furthermore, an Al-OC chemical bonding layer with a thickness of 10-50 nm exists at the interface between the aluminum layer and the base film.

[0012] Furthermore, after 500 1C charge-discharge cycles, the probability of lithium dendrite puncture is ≤0.1%.

[0013] Compared to existing technologies, the method for forming a cube-textured aluminum layer on the surface of a composite aluminum current collector according to the present invention includes the following steps: Step S1, providing a polymer base film, wherein the surface of the polymer base film is plasma-treated to form active functional groups; Step S2, depositing an aluminum layer using magnetron sputtering or vacuum evaporation, with a vacuum degree of 0.5*10-Pa-5x10-3Pa and the polymer base film temperature controlled at 100℃-200℃; Step S3, controlling the aluminum deposition rate at 50nm / s-100nm / s, the deposition temperature at 50℃-200℃, and the deposition thickness at 0.5um-5um, so that the {100} crystal plane of the aluminum layer grows perpendicular to the surface of the polymer base film, and so that... <100> The crystal orientation is aligned along the mechanical direction of the polymer base film; step S4: annealing is performed at 100℃-200℃ under an inert atmosphere for 10min-30min. This yields a composite aluminum current collector. The composite aluminum current collector prepared by the above method possesses high electrical and thermal conductivity. When used in batteries, it can reduce the battery's internal resistance and improve battery safety. Attached Figure Description

[0014] Figure 1 This is a flowchart of a method for forming a cube-textured aluminum layer on the surface of a composite aluminum current collector, provided by the present invention. Figure 2 The orientation distribution function (ODF) test results are calculated from the XRD pole figure data of the aluminum layer of the Cube textured composite aluminum current collector described in this invention. Detailed Implementation

[0015] To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0016] It should be noted that when a component is referred to as being "mounted on," "fixed to," or "set on" another component, it can be directly on the other component or may have an intervening component present. When a component is referred to as being "connected to" another component, it can be directly connected to the other component or may have an intervening component present.

[0017] It should also be noted that the directional terms such as left, right, up, and down in the embodiments of the present invention are only relative concepts or are based on the normal use state of the product, and should not be considered as restrictive.

[0018] Existing composite aluminum current collectors suffer from high surface interfacial contact resistance, leading to localized overheating during fast charging and a risk of thermal runaway. To address this, the inventors propose a method for forming a cube-textured aluminum layer on the surface of a composite aluminum current collector, comprising the following steps: Step S1, providing a polymer base film, the surface of which is treated with plasma to form active functional groups. The purpose of step S1 is to form active functional groups on the surface of the polymer base film, thereby improving the adhesion between the polymer base film and the metal layer. Specifically, a plasma treatment device is used to form a metal layer on the surface of the polymer base film. The plasma treatment device includes an atmospheric pressure plasma processing machine and a vacuum plasma processing machine. Specifically, the principle of forming active functional groups on the surface of the polymer base film through plasma treatment is as follows: the plasma treatment device generates plasma by ionizing oxygen molecules in the air. Its main purpose is to generate hydrophilic functional groups through the reaction of ions, electrons, and free radicals in the plasma in contact with the material surface, thereby improving the adhesion and wettability of the material.

[0019] Furthermore, the method for forming a cube-textured aluminum layer on the surface of the composite aluminum current collector also includes step S2, which involves depositing an aluminum layer using magnetron sputtering or vacuum evaporation at a vacuum level of 0.5*10⁻³ Pa - 5x10⁻³ Pa, and controlling the polymer base film temperature between 100℃ and 200℃. Using a vacuum level of 0.5*10⁻³ Pa - 5x10⁻ Pa can completely block oxidation contamination. Experiments have shown that when the vacuum level is greater than 5x10⁻³ Pa, the oxygen content of the aluminum layer increases, which leads to a decrease in the conductivity of the composite aluminum current collector. A vacuum level less than 0.5*10⁻³ Pa, on the other hand, leads to increased costs. Controlling the polymer base film temperature between 100℃ and 200℃ ensures the production of the cube-textured aluminum layer. This is because when the temperature exceeds 200℃, the surface migration rate of aluminum atoms becomes too high, leading to the formation of abnormal grains. Furthermore, excessively high temperatures can affect the polymer base film of the composite aluminum current collector, potentially making it brittle. Temperatures below 100℃ will cause the dominant texture type of composite aluminum current collectors to change to other types.

[0020] Furthermore, the method for forming a cube-textured aluminum layer on the surface of the composite aluminum current collector further includes step S3, which involves controlling the aluminum deposition rate to 50 nm / s-100 nm / s, the deposition temperature to 50℃-200℃, and the deposition thickness to 0.5 μm-5 μm, so that the {100} crystal plane of the aluminum layer grows perpendicular to the surface of the polymer base film, and so that... <100> The crystal orientation follows the mechanical direction of the polymer base film, forming an aluminum layer film with a cube texture as the main texture. In step S3, the deposition process used controls the aluminum deposition rate to 50nm / s-100nm / s, the deposition temperature to 50℃-200℃, and the deposition thickness to 0.5μm-5μm. The purpose is to ensure that the {100} crystal plane of the aluminum layer grows perpendicular to the surface of the polymer base film, and to make... <100> The crystal orientation follows the mechanical direction of the polymer base film, thereby forming an aluminum layer film with a cube texture as the main texture. In other words, by setting the above process conditions, a composite aluminum current collector with a cube texture as the main texture can be obtained.

[0021] Preferably, further, the method for forming a cube-textured aluminum layer on the surface of the composite aluminum current collector further includes step S4, which is: annealing at 100℃-200℃ in an inert atmosphere for 10min-30min to further enhance the orientation of the cube texture in the aluminum film. That is, the purpose of step S4 is to further enhance the orientation of the cube texture in the aluminum film, mainly by adjusting the process, which is accomplished by adding an annealing process to the existing conventional process for preparing composite aluminum current collectors. Thus, through the processes of steps S1, S2, S3, and S4, the composite aluminum current collector of step S5 can be obtained. Therefore, through the above method, a composite aluminum current collector with the following advantages can be obtained: 1. Significantly improved electrical and thermal conductivity, due to the... <100> The crystal orientation contributes to its good electrical and thermal conductivity. The cube texture creates numerous parallel alignments within the aluminum layers. <100> 1. **Crystal-oriented channels:** These channels reduce electron transport resistance and interfacial contact resistance, whereas traditional composite aluminum foils often experience a 10%-20% increase in resistance due to the insulation properties of the polymer substrate. 2. **Suppression of Joule heating:** High conductivity alleviates localized overheating caused by excessive resistance during fast charging, reducing the risk of thermal runaway. 3. **Optimized electrode processing performance:** This reduces the risk of cracking and enhances ductility. 4. **Further enhanced safety performance:** The Cube texture exhibits highly regular surface atomic arrangement, reducing lithium deposition stress concentration and suppressing dendrite penetration of the polymer layer.

[0022] Preferably, the polymer base film is polyethylene terephthalate or polypropylene with carboxyl groups grafted onto its surface, and a surface roughness Ra ≤ 200 nm. This has the advantage of eliminating stress concentration and improving interfacial adhesion. This is because when Ra > 200 nm, pores will form at the grooves during aluminum deposition due to the shadowing effect, resulting in low interfacial adhesion energy. At the same time, when the polymer base film with Ra ≤ 200 nm makes the aluminum layer density > 99.9%, it can eliminate micron-sized pores / cracks. In this way, lithium dendrites cannot penetrate the polymer layer along defect channels, improving the safety performance of the battery.

[0023] Furthermore, the orientation distribution function (ODF) of the composite aluminum current collector layer after annealing was calculated using XRD pole figure data. Diffraction intensity distribution tests were conducted at sample tilt angles ranging from 30° to 75°. At tilt angles ≥ 50°, the measured cube texture volume fraction exceeded 80%. At tilt angles ≥ 50°, the cube texture volume fraction tended to stabilize at this angle, resulting in relatively small overall test error. A volume fraction ≥ 80% reflects the proportion of cube texture in the aluminum layer, meaning that at this point {100} <100> Orientation refers to the alignment direction of the principal crystal planes. <100> The highly uniform crystal orientation results in low resistance to electron migration paths and enhanced conductivity. It also improves the yield rate of subsequent electrode processing because the Cube-textured aluminum layer exhibits consistent ductility in the MD / TD directions.

[0024] Furthermore, using the XRD Scherrer equation, the grain size of the aluminum layer was calculated to be 10nm-50nm, with a grain boundary orientation difference angle ≤10° accounting for >90%. If the aluminum layer grain size is greater than 50nm, the grains are too large, resulting in insufficient grain boundaries and long dislocation slip distances. In subsequent lithium battery applications, stress concentration occurs during the rolling of the cathode material, ultimately leading to microcracks on the aluminum foil surface during rolling. Conversely, if the aluminum layer grain size is less than 10nm, the grains are too small, resulting in excessively high grain boundary density, intensified electron scattering, and increased resistivity. A grain boundary orientation difference angle ≤10° accounting for >90% helps to further reduce the resistivity of the aluminum layer on the composite aluminum current collector.

[0025] On the other hand, the present invention also provides a cube-textured composite aluminum current collector, which is prepared by the method of forming a cube-textured aluminum layer on the surface of the composite aluminum current collector. The cube-textured composite aluminum current collector includes a polymer base film and a surface aluminum layer, wherein the proportion of cube-oriented grains in the aluminum layer is ≥80%; the deviation between the {100} crystal plane of the aluminum layer and the normal of the polymer base film surface is ≤5°; the aluminum layer... <100> The angle between the crystal orientation and the mechanical direction of the current collector is ≤10°. When the deviation between the {100} crystal plane of the aluminum layer and the normal of the polymer base film surface is ≤5°, the crystal orientation is basically parallel to the surface of the polymer base film, which can establish an ultra-high-speed channel for electrons and is beneficial to reducing the resistivity of the aluminum layer on the composite aluminum current collector. <100> An angle ≤10° between the crystal orientation and the mechanical direction of the current collector can induce directional lithium-ion deposition and reduce lithium dendrites. The proportion of cube-oriented grains in the aluminum layer is ≥80%, which improves the conductivity of the cube-textured composite aluminum current collector. Preferably, the conductivity ratio of the cube texture (Ω·m) of the composite aluminum current collector in the RD direction to that in the TD direction (where the resistivity of the aluminum layer is ≤3.5x10) is 0.95-1.05. The RD direction is the direction of travel of the composite aluminum current collector in the vacuum coating equipment, which can be referred to as the length direction of the composite aluminum current collector, while the TD direction is perpendicular to the direction of travel of the composite aluminum current collector in the vacuum coating equipment, which can be referred to as the width direction of the composite aluminum current collector. The advantage of this approach is that it solves the problem of localized overheating during fast charging. When the conductivity ratio is >1.1, the current concentrates in the RD direction, leading to ohmic heat accumulation and subsequent heating. Furthermore, it improves the cycle life of batteries using the composite aluminum current collector described in this invention. If the conductivity is outside the aforementioned range, excessive lithium ion embedding in the RD direction causes localized stress concentration, resulting in pulverization of the active material. Preferably, an Al-OC chemical bonding layer with a thickness of 10nm-50nm exists at the interface between the aluminum layer and the polymer base film. This is mainly achieved through the following method: First, the polymer base film is treated with plasma to generate hydroxyl or carboxyl groups on its surface. After treatment, when aluminum metal is formed on the polymer base film, it forms Al-O-OC chemical bonds with the hydroxyl or carboxyl groups. This reduces lithium dendrite formation because lithium dendrites are passivated in the Al-O-℃ layer. This is because lithium ions react with Al-OC to form LAO and carbon, thus reducing lithium dendrite formation. However, if the thickness of the Al-O-℃ chemical bonding layer is less than 10 nm, it will lead to discontinuity in the bonding layer, resulting in residual porosity that allows electrolyte to penetrate into the composite aluminum current collector and damage the polymer base film. Conversely, if the thickness of the Al-O-℃ chemical bonding layer is greater than 50 nm, it will increase the internal stress of the aluminum layer, leading to cracking.Preferably, when the Cube textured composite aluminum current collector is applied to a battery, the probability of lithium dendrite puncture is ≤0.1% after 500 1C charge-discharge cycles.

[0026] In summary, this invention provides a method for forming a cube-textured aluminum layer on the surface of a composite aluminum current collector. The method comprises the following steps: Step S1: Providing a polymer base film, the surface of which is subjected to plasma treatment to form active functional groups; Step S2: Depositing an aluminum layer using magnetron sputtering or vacuum evaporation, with a vacuum level of 0.5*10⁻³ Pa - 5x10⁻³ Pa and the polymer base film temperature controlled at 100℃-200℃; Step S3: Controlling the aluminum deposition rate at 50nm / s-100nm / s, the deposition temperature at 50℃-200℃, and the deposition thickness at 0.5μm-5μm, ensuring that the {100} crystal plane of the aluminum layer grows perpendicular to the surface of the polymer base film, and ensuring that... <100> The crystal orientation is aligned along the mechanical direction of the polymer base film; Step S4: Annealing is performed at 100℃-200℃ under an inert atmosphere for 10-30 minutes. This is because aluminum... <100> The crystal orientation is the optimal direction for its electrical and thermal conductivity. The cube texture allows for the formation of numerous parallel alignments within the aluminum layers. <100> Crystalline channels can reduce electron transport resistance and decrease interfacial contact resistance.

[0027] It is understood that those skilled in the art can make equivalent substitutions or modifications to the technical solution and inventive concept of the present invention, and all such substitutions or modifications should fall within the protection scope of the appended claims.

Claims

1. A method of forming a layer of Cube textured aluminum on the surface of a composite aluminum current collector, characterized by, The method comprises the following steps: Step S1, providing a polymer substrate, the surface of which is treated by plasma to form active functional groups; Step S2, depositing an aluminum layer by magnetron sputtering or vacuum evaporation, the vacuum degree being 0.5*10-3Pa-5*10-3Pa, and the temperature of the polymer substrate being controlled at 100-200; Step S3, controlling the deposition rate of aluminum to be 50-100nm / s, the deposition temperature to be 50-200, and the deposition thickness to be 0.5-5μm, so that the {100} crystal plane of the aluminum layer is perpendicular to the surface direction of the polymer substrate, and the <100> crystal direction is oriented along the mechanical direction of the polymer substrate; Step S4, performing annealing treatment at 100-200 under an inert atmosphere, and keeping the temperature for 10-30 minutes.

2. The method of claim 1, wherein the Cube textured aluminum layer is formed on the surface of the composite aluminum current collector. In step S2, the temperature gradient of the polymer substrate is controlled to be ±5℃ / cm; in step S3, the deposition rate of the aluminum thin film is controlled to be 50-100nm / s, and the deposition temperature is controlled to be 50-200, so that the high temperature promotes the migration of aluminum atoms and the directional arrangement of crystal grains.

3. The method of claim 1, wherein the Cube textured aluminum layer is formed on the surface of the composite aluminum current collector. The polymer substrate is polyethylene terephthalate or polypropylene with carboxyl groups grafted on the surface, and the surface roughness Ra is ≤200nm.

4. The method of claim 1, wherein the Cube textured aluminum layer is formed on the surface of the composite aluminum current collector. After annealing, the Cube texture of the aluminum layer of the composite aluminum current collector is tested by calculating the orientation distribution function of the XRD pole figure data, the diffraction intensity distribution is tested at a sample tilt angle of 30-75, and when the tilt angle is ≥50, the Cube texture volume fraction is more than 80%.

5. The method of claim 4, wherein the Cube weave aluminum layer is formed on the surface of the composite aluminum current collector. The grain size of the aluminum layer is calculated by XRD Scherrer formula to be 10-50nm, and the proportion of the grain boundary orientation difference angle ≤10 is >90%.

6. A cube weave composite aluminum current collector comprising a polymer base film and a surface aluminum layer, characterized in that, The Cube orientation accounts for the main part of the aluminum layer grains; the {100} crystal plane of the aluminum layer deviates from the normal direction of the polymer substrate surface by ≤5.

7. The Cube texture composite aluminum current collector according to claim 6, wherein the <100> crystal direction of the aluminum layer deviates from the mechanical direction of the current collector by ≤10.

8. The Cube texture composite aluminum current collector of claim 6, wherein, The in-plane resistivity of the aluminum layer is ≤ 3.5 x 10⁻⁷ 8 Ω·m, and the ratio of the conductivity in the RD direction and the TD direction of the composite aluminum current collector is 0.95-1.

05.

9. The Cube texture composite aluminum current collector of claim 6, wherein, There is an Al-O-C chemical bonding layer with a thickness of 10-50nm at the interface between the aluminum layer and the substrate.

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